Outbreaks of severe dorsal skin lesions in Swedish moose (Alces alces)

From early autumn to mid-winter 2015, there was a notable increase in cases of moose (Alces alces) with severe skin lesions were reported by hunters to the National Veterinary Institute in Uppsala, Sweden. Lesions consisted of... [ view full abstract ]

From early autumn to mid-winter 2015, there was a notable increase in cases of moose (Alces alces) with severe skin lesions were reported by hunters to the National Veterinary Institute in Uppsala, Sweden. Lesions consisted of extensive, deep suppurative dermatitis covered by dry crusts. Similar lesions have been reported earlier but only as sporadic cases. A systematic collection of samples and whole carcasses was initiated, including subsequent histo-pathologic and microbiologic analyses in order to further investigate underlying causes. Hunters were also asked to submit moose observation indexes in order to estimate population effects. Until mid-January 2016, 150 reports had been recorded and 45 cases submitted for analysis. The majority of reports (99.3 %, n=149) were adult males. Lesions were noted primarily along the dorsal lumbar and sacral areas of the body, in severe cases extending forward to the neck and ventrally on the torso. In affected areas, an acute-chronic active dermatitis with ulceration, crusting, and a mixed inflammatory response (neutrophils, eosinophils, lymphocytes and plasma cells) and marked thickening of the dermis due to fibrosis was noted. Deer ked (Lipoptena cervi) were observed in high numbers, but not quantified. The major bacterial finding was Staphylococcus aureus in 40/45 samples (89 %). Pan-herpes PCR of skin (n=12) and dorsal root ganglia (n=1) was negative. Moose observation card reports show cases distributed over a large geographic area in southern Sweden (~100,000 km2). The etiology and possible underlying factors are under current investigation.